Answer:
Bottle neck stations our the ones which take more time than the previous station because of which units received per hour our more than units created per hour creating a bottleneck.
In this case Station 2 is taking more time than station 1. (10>9)
Station 3 has 2 machines so although one machine takes more time than station one because of having 2 machines the time can be divided by 2 so there is no bottle neck here. (6<10)
Station 4 takes less time than station 2. (5<6)
Station 5 takes more time than station 4. (8>5) but station 5 is not a bottle neck because it is the last station so it is not slowing the units from going on to another station or the next station, because the good is finished here there is no bottle neck
The only bottle neck is station 2 because it takes more time to send one unit to the next unit compared to receiving one unit from station 1.
Explanation: